June 2015

Weed Control: Caltrop

Introduction

Caltrop (Tribulus terrestris) is a summer growing annual weed which produces sharp, spiny fruits. The spiny burr is similar to three corner jack, but they are different plants. Caltrop will grow in almost any soil type and grows rapidly after summer rains. Staggered germinations make control of caltrop very difficult.

The burrs of caltrop contain the seed which can remain viable for many years, and can become a problem if not controlled at the early stages. Your involvement is essential to control caltrop.

General Control Advice

Prevention

The best strategy is to keep caltrop off the property. Any plants found should be destroyed before setting seed to prevent infestation. Continued vigilance on the property for new outbreaks is required to prevent the establishment of this weed.

The key to controlling any weed population is to prevent the plants from reproducing. For caltrop, this means preventing the seed from setting. The suggested methods below should be timed to achieve this goal – killing the plant at the end of its season will not help control the infestation.

Mechanical

  • cultivate after each successive germination before the seed sets
  • for small infestations, hand weed or use a shovel to cut each plant off where it isattached at the central tap root. Generally small plants(without seeds) may be pushed out by the toe of your shoe
  • some of the seed may be gathered by lightly raking the area
  • once plants are removed and ground is exposed, use a prickle roller to remove mature fruits, or use high density foam (camping mattress) laid on the ground with weight applied to pick up burrs. This can then be carefully removed and the seed scraped off into a bin, allowing the mat to be reused
  • remove plants carefully from site (bag up and place in bin) making sure all burrs
    are collected

Chemical

Note new spot infestations so they can be checked for later germinations. For best results, herbicides should be applied to plants before setting seed, when actively growing and not under stress of any kind.

Spot spray with glysophate (Round-up or similar).

Mulch

Once caltrop has been cleared, wood chip (to a depth of 100mm) or various types of gravel mulch (to a depth of 50mm) may be applied. The area will then need to be monitored for further outbreaks.

Competition

Caltrop does not compete well with other groundcovers. The establishment of a small lawn, or planted garden areas will help crowd it out.

Staging

Where caltrop has spread over a large area, it is sometimes preferable to divide the yard into sections for the reason of staging the development over a period of time.

The areas may be used for different purposes, e.g. lawn, gravel or mulch, paving, garden beds and sprayed areas.

Once a section has been established the next area may be tackled. This will enable the development of some useable outside space in a relatively short period. It is important if doing this to control the remaining area by mechanical or chemical methods.

Reporting

Report outbreaks of caltrop to the Maintenance Centre by telephoning 131 288 between 7 am and 7 pm.


Housing SA, GPO Box 292 Adelaide SA 5001

General enquiries: 131 299*

Maintenance enquiries: 131 288

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